ELIA KAZAN: A LIFE; By Elia Kazan; Alfred A. Knopf; $24.95.

Autobiographies are noteworthy less for what they reveal than for what they conceal. Noel Coward produced three witty volumes of memoirs without ever mentioning his homosexuality; Michael Jackson's new autobiography is headed for the best-seller charts without telling us anything we really want to know."Elia Kazan - A Life," on the other hand, is a revelation of the first order, a brutally honest and piercingly illuminating look at one of America's most controversial men of arts and letters. It is, quite simply, the most compelling, readable and exciting autobiography I've ever read - a novelistic treatment crammed with racy episodes, famous people and psychological insights ranging from the painful to the transcendental. It runs for 848 pages, and I was sorry when it ended.

Kazan's life has been one of landmark achievements and bigger-than-life personalities. He got his first taste of show business in the 1930s with New York's left-leaning Group Theatre, for whom he created a pivotal role in Clifford Odets' "Waiting for Lefty."

Moving on to directing, he staged the original productions of "All My Sons" and "Death of a Salesman," "The Skin of Our Teeth," "A Streetcar Named Desire," "JB" and "Tea and Sympathy."

Expanding into film, he had substantial hits in "A Tree Grows in Brooklyn," "Gentleman's Agreement," "On the Waterfront," "Viva Zapata!" "East of Eden" and "Splendor in the Grass."

Fed up with meddlesome producers, he turned to writing, publishing such best-sellers as "The Arrangement." Along the way he helped found the famed Actors' Studio and the ill-fated Lincoln Center Repertory Company and sparked a national uproar when he became a friendly witness for the House Un-American Activities Committee, "naming names" of his former Communist Party comrades working in films.

Given the spectacular nature of his life, Kazan's memoirs would be noteworthy even if they were merely his recollections of famous people. Kazan's list of colleagues, lovers and enemies reads like a who's who of the arts: Marlon Brando, Tallulah Bankhead, John Steinbeck, Marilyn Monroe, Darryl F. Zanuck, Arthur Miller, Lee Strasberg, John Garfield, Harold Clurman, Clifford Odets, Tennessee Williams, Lillian Hellman . . . the list threatens to be endless.

But there's much, much more. The great strength of "Elia Kazan - A Life " is its story of a man coming to grips with himself, engaged on a lifelong quest through radical politics, sexual excess and the artistic imperative. At the age of 78, Kazan is trying to understand why he did what he did. He conjures up long-ago emotions and impressions, sifting through them from the perspective of years and maturity in a remarkably objective attempt to arrive at the "truth" about himself.

Yes, Kazan remains defiant, and he sometimes tries to justify his actions - but he never whitewashes. A reader leaves this book occasionally horrified by the author's behavior, but invigorated by his honesty.